Natural fiber treatment process

ABSTRACT

The invention refers to a natural fiber treatment process in order to enable the fibers to be conditioned for optimal yarn production, and subsequently of base fabrics. The process comprises the stages of an alkaline treatment, bleaching and the addition of a softening agent.

FIELD OF INVENTION

The present invention lies within the textile sector, particularly in processes of natural fiber treatment for different applications.

PRIOR ART

At present, the leaves of the Aspargaceae family are considered to be a variety of fibrous plant materials with a high potential for exploitation in the textile industry. Usually, these vegetable materials have a high content of cellulose that may be used in the manufacture of base fabrics for clothing. However, its use as raw material in the production of base fabrics is limited due to its low fiber fineness and roughness, due to the presence of non-cellulosic components, which does not make it suitable for yarns that may be spun with traditional machinery for the production of base fabrics.

With the rise of the study of new applications involving natural coarse fibers, the most recent advances have focused on developing cottonization processes, which refer to the processing of coarse or hard fibers to make them similar to cotton fibers in their properties (e.g. length, softness, diameter or fineness). This cottonization is achieved by removing all or part of the pectins, lignin and hemicellulose without damaging the fiber cellulose and separating the elemental fibers that are bound together by these compounds.

Prior art describes natural fiber treatment processes of the Poaceae, Urticaceae, Malvaceae, Linaceae, Gramineae, Fabaceae, Cannabaceae families, with which fibers are obtained with different properties and features. Disclosed processes generally include alkaline treatment, bleaching and drying stages.

U.S. Pat. No. 7,481,843 B2 describes a procedure for the extraction and preparation of coarse ramie (Urticaceae family), jute (Malvaceae family) and hemp (Cannabaceae family) fibers for the production of fine, pure yarns, in which the conventional spinning system is fed 100% with the selected fiber, or mixed, in which different fibers are mixed in the desired proportions before the card processing and whereby an intimate mixture yarn is obtained at the end of the spinning process.

U.S. Pat. No. 5,718,802 discloses the use of the sugar cane by-product (Poaceae family) for the production of yarns and nonwovens, in which an alkaline treatment with NaOH (caustic soda) and heating is used to extract the fibers. Combined mechanical treatments such as steam explosion, pressure gas bubbles, strong boiling, among others, are also used.

US20070199669 discloses a method for the extraction of cellulosic fibers from the leaves and stems of corn, grass, rice, barley (Poaceae family), sorghum, wheat (Gramineae family), soybean (Fabaceae family) and cotton stems (Malvaceae family), by means of an alkaline treatment to partially delignify the material and a subsequent enzymatic treatment to extract the fibers.

U.S. Pat. No. 7,624,478 B2 describes a method for processing coarse fibers derived from the cotton stalk (Malvaceae family), including extraction, degumming, preservation, cutting, opening, carding, grading and packaging. U.S. Pat. No. 7,526,837 B2 discloses a process for the treatment of flax fibers (Linaceae family), which consists of cleaning, cottonization, retting and drying of the raw material by means of an electro-hydraulic process.

U.S. Pat. No. 4,359,859 B2 describes a thread formed from the fibers of corn leaves and pods, by immersing the leaves and pods in a solution of caustic soda for their release and then, dried, carded and spun. CN101041916 (A) describes a process for obtaining a yarn from a mixture of bamboo fiber (Poaceae family) and ramie (Urticaceae family).

In the extraction and preparation of Aspargaceae family fibers, improper processing can damage fibers to a large extent, resulting in low fiber yield and economic losses. Therefore, there is a need to design procedures for the extraction and preparation of fibers from the Aspargaceae family in order to obtain fibers suitable for the production of high quality fabrics for clothing.

The invention process allows us to obtain natural fibers for new base fabrics for the diversification of their applications in clothing, expanding the portfolio of opportunities for these fibers within the textile world.

BRIEF DESCRIPTION OF THE INVENTION

The process of the present invention makes it possible to obtain modified natural fibers from the leaves of the Aspargaceae family, by adding a softening agent to the natural fibers after they have undergone alkaline and bleaching treatment. The fibers obtained exhibit excellent tactile properties due to the removal of non-cellulosic components, favoring the decrease of the fiber diameter and the increase of their flexibility.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Photograph of natural fiber (a) and cottonized fiber (b).

FIG. 2. Scanning electron microscope (SEM) images of natural fiber (a) and cottonized fiber (b).

FIG. 3. Photograph of a cotton/fique mixture yarn (1:1).

FIG. 4. Fabric photograph produced with a cotton/fique cottonized blended yarn (1:1).

DETAILED DESCRIPTION OF THE INVENTION

Hard fibers from the leaves of the Aspargaceae plant are primarily composed of cellulose (between 40-70%), hemicellulose, pectins and lignin, in charge of agglutinating and maintaining the integrity of the cellulose fibers. These other non-cellulosic components are responsible for these fibers being coarse, hardly flexible, and with low hygroscopicity. These components must be removed with chemical, mechanical, enzymatic and/or physical cottonizing treatments to obtain softer and more individualized fibers with applications in the textile sector.

Thus, the present invention refers to a process for the treatment of natural fibers coming from the Aspargaceae family, among them, fique, henequen and sisal, the leaves and stems of which are initially defibrated and whose fibers cut lengthwise in sizes between 10 mm and 1500 mm.

Once the fibers have been shredded and cut, they are subject to an alkaline treatment that consists of submerging them in an alkaline solution of KOH or NaOH (1-20% w/w), with a fiber/alkaline solution ratio between 1:5 and 1:50, at a temperature between 20 and 90° C., for 1 to 24 hours. In an embodiment of the invention process, the fibers are immersed in an alkaline solution of NaOH between 10% and 15% (w/v), at a fiber/solution ratio between 1:20 and 1:40, at a temperature between 60° C. and 80° C., for 1 to 5 hours. In another embodiment of the invention process, the fibers are immersed in a 15% (w/v) solution of KOH at a temperature of 80° C., for 2 hours.

The fibers obtained are rinsed one or more times with water and subject to a bleaching phase, which can be carried out by chemical treatment or enzymatic treatment at a temperature between 20° C. and 90° C., for 0.1 to 168 hours, after which the fibers are rinsed again with water. In one embodiment of the invention process, the bleaching phase is carried out using a chemical treatment at a temperature between 60° C. and 90° C., for 0.5 to 3 hours, preferably at a temperature of 80° C. for 2 hours.

For the purposes of the present invention, the chemical treatment of the bleaching phase comprises adding a bleaching agent, a strong base, a catalyst and an anti-foaming agent to the fibers. The bleaching agent is selected from chemical compounds such as chlorine in any state, compounds and/or salts derived from chlorine (e.g. sodium hypochlorite), sulfides or sulfuric compounds, oxygen or ozone or compounds releasing oxygen such as peroxides, perborates, persulfates or perchlorates, alkaline metals, alkaline earth metals, ammonium compounds, and mixtures thereof, in concentrations ranging from 1% to 30% (w/v). In one embodiment herein, the bleaching agent is hydrogen peroxide.

The strong base that is added in the bleaching phase may be NaOH or KOH, at concentrations between 0.1 and 5% (w/w); the catalyst is selected from inorganic salts, hydrocarbons, alcohols, organic acids and their derivatives, in concentrations between 0.01 and 1.0%; and the anti-foaming agent is selected from siliconized, non-siliconized emulsions or stearic derivatives of alcohols or siloxanes, in concentrations between 1.0% and 10.0%. In an embodiment of the invention process, the strong base is NaOH, the catalyst is magnesium sulfate, the bleaching agent is hydrogen peroxide and the anti-foaming agent is a stearic alcohol.

The enzymatic bleaching treatment consists of adding to the natural fibers one or more enzymes such as: peroxidases, laccases, catalase oxidases, pectinases, cellulases, at concentrations between 1 and 100 g/L, at a temperature between 20 and 60° C., for a time between 1 and 168 hours. In an embodiment of the invention, enzymatic treatment is carried out by the addition of peroxidases and cellulases at concentrations between 0.01 and 5% (v/v) at temperatures between 20° C. and 40° C., for 1 to 168 hours. In another embodiment of the invention, enzymatic treatment is carried out by the addition of peroxidase at a concentration of 0.3 (v/v), temperature of 25° C., for 168 hours.

Once the bleaching phase is finished, a softening agent selected from cationic, anionic, non-ionic, reactive, amphoteric, siliconized or enzymatic emulsions is added to the fibers in order to provide softness to the fiber and to avoid cellulose baking, which would hinder the brush process, in which the fiber is opened, separated and cleaned of dirt and short fibers, in order to be individualized and parallelized to form a veil which will be converted into carding tape at the end of the process.

The softening agent has a concentration between 0.1% and 10%, preferably between 0.5% and 2.0% and is added to the fibers at a temperature between 30° C. and 80° C., with a fiber/solution ratio between 1:5 and 1:50 and for a period of time between 0.5 and 2 hours. In one embodiment of the invention, the softening agent is a siliconized nanoemulsion at a concentration of 1.0%, the fiber/solution ratio is 1:40, and the temperature is 60° C., for one hour.

Finally, the fibers can undergo a drying stage, which can be carried out at room temperature (15° C. to 25° C.) or by convection in an oven at a temperature between 40° C. and 80° C., for 0.5 to 36 hours.

The fibers obtained through the invention process have similar features to cotton fiber, such as soft touch, white color, greater flexibility and finesse. Having these features, the fiber can be mixed intimately with other fibers such as cotton, and with all types of artificial and synthetic fibers in the production of fine yarns, which facilitate the production of base fabrics that may be used in clothing, accessories, upholstery and decoration in general.

The following Examples illustrate the invention, without the inventive concept being restricted thereto.

Example 1. Treatment of Fique Fibers

Fique fibers with a length of 35 mm were cut using a guillotine. The fibers were subject to an alkaline process at 80° C. for 2 hours, using a solution of 666.6 g of potassium hydroxide and 3333.3 ml of water.

Subsequently, the fibers were rinsed and the bleaching phase was carried out, in which 2918 ml of water, 80 g of caustic soda at a concentration of 90%, 2.0 g of magnesium sulfate, 200 g of antifoam (stearic alcohol) and 800 g of hydrogen peroxide in a concentration of 10% (w/w) were added.

The solution obtained was taken to a temperature of 80° C., kept for one hour and then the fibers were rinsed 3 times by overflow. Finally, the fiber was subject to a softening process, for which a solution was prepared with 3920 ml of water and 80 g of a siliconized nanoemulsion. This solution was taken to a temperature of 60° C. in order to add the fiber and run it through the process for one hour. The resulting cottonized fiber was dried in an oven at 40° C. for 24 hours.

Example 2. Treatment of Fique Fibers

Fique fibers with a length of 35 mm were cut using a guillotine. The fibers were subject to an alkaline process at 60° C. for 0.5 hours, using a solution of 222.2 g potassium hydroxide and 3777.7 ml water.

Subsequently, the fibers were rinsed and the bleaching phase was carried out, in which 2918 ml of water, 80 g of caustic soda at a concentration of 90%, 2.0 g of magnesium sulfate, 200 g of antifoam (stearic alcohol) and 800 g of hydrogen peroxide in a concentration of 10% (w/w) were added.

The solution obtained was taken to a temperature of 80° C., kept for one hour and then the fibers were rinsed 3 times by overflow. Finally, the fiber was subject to a softening process, for which a solution was prepared with 3920 ml of water and 80 g of a siliconized nanoemulsion. This solution was taken to a temperature of 60° C. in order to add the fiber and run it through the process for one hour. The resulting cottonized fiber was dried in an oven at 40° C. for 24 hours.

Example 3. Treatment of Sisal Fibers

Sisal fibers with a length of 35 mm were cut using a guillotine. The fibers were subject to an alkaline process at 80° C. for 2 hours, for which a solution of 666.6 g of potassium hydroxide and 3333.3 ml of water was used.

Subsequently, the fibers were rinsed and the bleaching phase was carried out, in which 2918 ml of water, 80 g of caustic soda at a concentration of 90%, 2.0 g of magnesium sulfate, 200 g of antifoam (stearic alcohol) and 800 g of hydrogen peroxide in a concentration of 10% (w/w) were added.

The solution obtained was taken to a temperature of 80° C., kept for one hour and then the fibers were rinsed 3 times by overflow. Finally, the fiber was subject to a softening process, for which a solution was prepared with 3920 ml of water and 80 g of a siliconized nanoemulsion. This solution was taken to a temperature of 60° C. in order to add the fiber and run it through the process for 1 hour. The resulting cottonized fiber was dried in an oven at 40° C. for 24 hours.

Example 4. Characterization of Fique Fiber

The following characterization tests were performed on fique fibers obtained according to Example 1: length, diameter, tensile strength, final lignin content, final cellulose content, final hemicellulose content (Table 1).

TABLE 1 Property Range Length 20-35 mm Fineness/Diameter 54-125 mm Tensile strength 48-257 MPa Lignin content 4.2-7.6% Cellulose content  60-80% Hemicellulose content 0.0-13.5% 

Example 5. Obtaining Yarn from Fibers of Fique

From fique fibers obtained according to Example 1, a spun yarn was obtained with a composition of cottonized cotton/fique (1:1). In order to obtain this yarn, 28 mm cotton with a fineness of 3.6 micronaire was selected. The fibers were mixed in a ratio of 50/50, they were run through the opening process in a Shirley carding machine, in which fixed plate cards were used.

The carding tape was run three consecutive times through the draw frame in order to regulate the mass of the tape, which had a basis weight of 3.3 g/m. The resulting draw tape was processed in an industrial electro-jet burner in order to obtain a 0.850 g/m wick. Finally, a single-line thread was obtained on a 520 turns/meter Z-twist Pinter ring spinning machine with a Ne 14 count.

Example 6. Obtaining the Base Fabric

From threads obtained according to Example 5, a base fabric was obtained which was produced on a Jacquard loom. The loom, previously warped with polyester cotton yarn and cotton/fique cottonized yarn (1:1), was inserted into the weft. Flat weave was produced in the taffeta, serge and satin ligaments. 

1) A process for treating natural fibers comprising the following stages: (a) subjecting the natural fibers to alkaline treatment; (b) subjecting the fibers obtained in stage (a) to a bleaching phase; and (c) adding a softening agent to the fibers obtained in stage (b). 2) process according to claim 1, wherein the natural fibers are from the Aspargaceae family. 3) process according to claim 2, wherein natural fibers are selected from sisal, Pique, henequen and abaca. 4) process according to claim 1, wherein the alkaline treatment of stage (a) is carried out by incorporating the natural fibers in a solution of NaOH or KOH 15% (w/v) at a temperature between 25° C. and 100° C. and a time period between 0.1 and 24 hours. 5) process according to claim 1, wherein the bleaching phase of stage (b) is carried out by chemical treatment or enzymatic treatment. 6) process according with claim 1, wherein the bleaching phase of stage (b) is carried out by adding an anti-foaming agent, a strong base, a catalyst and a bleaching agent, maintaining a temperature between 20° C. and 100° C., for a period of time between 0.1 and 24 hours. 7) process according to claim 6, wherein the anti-foaming agent is a stearic derivative of alcohols or siloxanes, the strong base is NaOH or KOH. 8) process according to claim 6, wherein the catalyst is selected from inorganic salts, hydrocarbons, alcohols, organic acids and derivatives thereof. 9) process according to claim 6, wherein the bleaching agent is selected from hydrogen peroxide, sodium chlorite, sodium hypochlorite and mixtures thereof. 10) process according to claim 1, wherein the bleaching process of stage (b) is carried out by means of an enzymatic treatment consisting of adding at least one ligninolytic enzyme selected from peroxidases, oxidases, laccases and mixtures thereof, at a temperature between 20° C. and 80° C. for 0.1 to 168 hours. 11) process according to claim 1, where the softening agent of stage (c) is selected from silicones, silicone emulsions, silicone nanoemulsions, ligninolytic enzymes and mixtures thereof. 12) process according to claim 1, which additionally includes a drying stage, carried out at a temperature between 15° C. and 80° C. 13) Natural fibers obtained through the process of claims 1 to 12, characterized by the following properties: Property Range Length 20-35 mm Fineness/Diameter 54-125 mm Tensile strength 48-257 MPa Lignin content 4.2-7.6% Cellulose content  60-80% Hemicellulose content  0-13.5% 